Grain boundary grooving in thin film under the influence of an external magnetic field: A phase-field study

TL;DR

This study uses a phase-field model to analyze how external magnetic fields influence grain boundary grooving and grain growth in thin films, revealing steady-state behaviors, universal surface profiles, and potential for magnetic field-assisted texture control.

Contribution

It introduces a phase-field simulation of magnetic field effects on grain boundary grooving and grain growth, highlighting steady-state behavior and universal surface profiles.

Findings

Steady-state grain boundary motion above a critical magnetic field.

Universal, time-invariant surface profiles matching Mullins theory.

Magnetic field influences grain growth and reduces pitting at grain vertices.

Abstract

Using a phase-field model, we study the surface diffusion-controlled grooving of a moving grain boundary under the influence of an external magnetic field in thin films of a nonmagnetic material. The driving force for the grain boundary motion comes from the anisotropic magnetic susceptibility of the material, leading to the free energy difference between differently oriented grains. We find that above a critical magnetic field the grain boundary motion is in a steady state, and under this condition, the mobile thermal groove exhibits a universal behavior scaled surface profiles are timeinvariant and independent of thermodynamic parameters. The simulated universal curve agrees well with Mullins theory of mobile grooves for any groove shape. We extend our study to a three-dimensional polycrystalline thin film with equalsized hexagonal grains. We observe a preferential grain growth depending on the applied magnetic field direction, which can be leveraged for field-assisted texture control of polycrystalline thin films. Our study reveals that keeping other conditions the same, the rate of pitting at the vertices of the hexagonal grains substantially decreases in the presence of the external magnetic field.